Flame-retardant compositions for plastics



United States Patent 3,370,030 FLAME-RETARDANT COMPOSITIONS FOR PLASTICS Joseph Frederick Cannelongo, Piscataway, N.J., assignor to AmericanCyanamid Company, Stamford, Conn., a

corporation of Maine N0 Drawing. Filed Mar. 14, 1966, Ser. No. 533,797

8 Claims. (Cl. 260-285) This invention relates to flame-retardant compositions. More particularly, this invention relates to flame-retardant compositions comprising a combination of a diphosphine oxide and a chlorinated hydrocarbon material. Still more particularly, this invention relates to flame-retarded com positions comprising a thermoplastic polymer containing a flame-retarding amount of a synergistic combination of a chlorinated hydrocarbon material and a compound having the formula o o l (CH2)n l R R wherein R and R, individually, represent hydrogen, aryl (C -C alkyl (C -Cs), aralkyl (O -C cyanoalkyl (C -C carboxyalkyl (c '-c,), or carbamoylalkyl (C -C radicals, and n represents a Whole positive integer of from 1-4, inclusive, no more than one of R and R being hydrogen.

The use of certain additives for the purpose of reducing the flammability of various thermoplastic polymers is Well known to those skilled in the art. Among the additives currently employed for such a use are various specific types of phosphorus-containing compounds. These phosphorus compounds are generally used either alone or in combination with other materials such as aliphatic or aromatic antimonous compounds. Certain analogous materials such as chlorostyrene copolymers, chlorinated paraflin waxes, alone or with antimony oxide, are also known to be effective flame-retardants for resinous materials. One drawback of these known compounds and combinations of compounds, however, has been the fact that generally large amounts, i.e. upwards of 35%, of the additive must be incorporated into the polymer in order to render it reasonably flame-retardant. Such large quantities of additive oftimes deleteriously alter the properties of the polymer and moreover, some additives tend to crystallize or oil out of the polymer after a relatively short time of incorporation therein.

I have now found that superior flame-retarding properties can be imparted to thermoplastic polymers by incorporating into the polymer a synergistic combination or mixture of a chlorinated hydrocarbon material and a compound represented by Formula I, above. The novel synergistic combination provides improved flame-retardance over the additives of the prior art and, additionally, provides this superior result at materially lower concen trations than previously found to be necessary for the known additives.

The results shown by the use of the above-mentioned flame-retardant combination are surprising and unexpected in that the combination provides a greater degree of flameretardancy than one would expect from the results shown ice It is therefore an object of the present invention to provide flame-retardant compositions.

It is a further object of the present invention to provide flame-retardant compositions comprising a combination of a diphosphine oxide and a chlorinated hydrocarbon material.

It is still a further object of the present invention to provide flame-retarded compositions comprising a thermoplastic polymer containing a flame-retarding amount of a synergistic combination of a chlorinated hydrocarbon material and a diphosphine oxide represented by Formula I, above.

These and other objects of the instant invention will become more apparent to those skilled in the art upon reading the more detailed description set forth hereinbelow.

As mentioned above, the first critical component of our novel flame-retardant compositions is a chlorinated hydrocarbon material. Although any chlorinated hydrocarbon material tends, to some extent, to be effective, I have found that those which are stable to the processing conditions of thermoplastic polymers when in combination therewith are more preferable. That is to say, a critical limitation in regard to the chlorinated hydrocarbon materials is that they should have a boiling point of at least about 200 C., in that those of a lower boiling point tend to vaporize out of the polymer when the polymer is ultimately processed or fabricated for consumer production.

A further critical limitation in regard to the chlorinated hydrocarbon materials utilized herein is that they must contain at least about 40% of combined chlorine, preferably from about 40% to by Weight based on the weight of the compound per se. Percentages of combined chlorine above 80% are tolerable but impractical, while at percentages lower than about 40%, the effectiveness of the combination is materially lowered. The chlorinated hydrocarbon material may be used in concentrations ranging from about 0.2% to about 15.0%, by weight, based on the weight of the polymer to which it is added, preferably from about 0.5% to about 12.0%, same basis.

Examples of useful chlorinated hydrocarbon materials include compounds such as perchloropentacyclodecane,

hexachlorocyclopentadiene, hexachlorobenzene; the polychlorinated monocyclic aromatic hydrocarbons such as 2,3,5,6-tetrachloroo, m or p-xylene, 2,5-dichloroo, m or p-xylene, 0:,ot-(liChl0IO- o, m or p-xylene, c d-hexachloroo, m or p-xylene; various commercially available chlorinated biphenyls and polyphenyls which range in consistency from oily liquids to fine, white crystals to hard, transparent resins. These biphenyls and polyphenyls are non-oxidizing, have a low volatility and are noncorrosive. They are not hydrolyzed by water, alkalies or acids, are insoluble in water, glycerine and glycols and distill at 215 C. to 450 C. The crystalline materials have melting points up to 290 C. and the resins have softening points up to C.

A further class of applicable chlorinated hydrocarbon materials useful herein are the chlorinated parafiin waxes containing between about 40% to 80% combined chlorine and averaging from 18-36 carbon atoms. These materials are chlorinated soft or slack waxes and are set forth in one or more of the following US. Patent Nos. 2,924,532, 2,962,464 and 3,194,846, which patents are hereby incorporated herein by reference.

The second critical component of my novel flame retardant compositions is a diphosphine oxide represented by Formula I, above. These diphosphine oxides are suitable herein as long as they too are stable to the processing conditions of the polymer into which they are incorporated. They may be produced by any known procedure, such as those disclosed in US. Patent No. 3,032,589

and Issleib et al., Berichte, 92, 3175 (1954), which publications are hereby incorporated herein by reference.

For example, one procedure for the production of these diphosphine oxides comprises reacting an excess of a compound of the formula (II) R R P-(o112)..1 R! R! wherein n, R and R are as defined above in regard to Formula I, with H or oxygen to form the oxide. The reaction is maintained at reflux by the use of, for example, Dry Ice, and the resultant diphosphine oxide may then be isolated by filtration or by solvent evaporation. Yields usually are from 50% to 100% of the theoretical. These procedures, however, form no part of the present invention.

The diphosphine starting material from which the oxide is prepared, may be produced, for example, as described in articles by Chatt et al., J. Chem. Soc., p. 1378, 1960 or Hewertson et al., J. Chem. Soc., p. 1490, 1960.

The diphosphine oxide may be incorporated into the polymeric material in concentrations ranging from about 0.1% to about 15.0%, preferably 0.212.0%, by weight based on the weight of the polymer to which it is added.

The terms aryl radical and aralkyl radical, as used herein in regard to the substituents R and R of Formula I, above, are meant to include not only carbon hydrogen cyclic compounds but also lower alkyl, halogen and cyano ring-substituted cyclic compounds and the scope of the instant invention should be construed so as to include compounds falling within this definition.

Examples of substituted diphosphine oxides which may be used according to the instant invention include:

methylenebis (diphenyl phosphine oxide, methylenebis(dinaphthyl)phosphine oxide, ethylenebis dinaphthyl phosphine oxide, ethylenebis(diphenyl) phosphine oxide, propylenebis (ditolyl) phosphine oxide, propyleneb is dixylyl )phosphine oxide propylenebis diphenyl phosphine oxide,

- butylenebis dimethyl phosphine oxide,

methylenebis(diethyl) phosphine oxide,

ethylene bis(di-n-propyl)phosphine oxide, butylenebis diisopropyl phosphine oxide, methylenebis di-n-butyl phosphine oxide, ethylenebis(di-t-butyl)phosphine oxide, propylenebis (diisobutyl) phosphine oxide, butylenebis (dipentyl phosphine oxide, methylenebis dihexyl phosphine oxide, ethylenebis(dibenzyl)phosphine oxide, propylenebis[bis Z-phenethyl phosphine oxide], butylenebis[bis(3-phenylpropyl)phosphine oxide], methylene [bis(4-phenylbutyl)phosphine oxide], ethylenebis [bis (naphthylmethyl)phosphine oxide], butylenebis [bis (Z-carb amoylethyl phosphine oxide],

methylenebis[bis(2-carbamoyl-n-propyl)phosphine oxide],

methylenebis[3 ,4-dichlorobenzyl 3-carb oxyethyl phosphine oxide, butylenebis (phenyl) phosphine oxide, methylenebis (2 cyanoethyl) phosphine oxide, propylenebis 3-carboxypropyl phosphine oxide, butylenebis 3,4-difiuorobenzyl phosphine oxide, ethylenebis (p-bromophenethyl) phosphine oxide, butylenebis(benzyl)phosphine oxide, ethylenebis 3-cyanopropyl phosphine oxide, butylenebis(4-chlorobenzyl)phosphine oxide,

and the like.

Any thermOplastic polymeric material may be rendered flame-retardant by the incorporation therewith of the above-identified flame-retardant combinations. Specifically, however, the vinyl type polymers, wherein a monomeric material is polymerized, by known methods, e.g. by use of free-radical generating catalysts, irradiation, anionic and cationic catalysts, etc. are those preferred. Examples of the vinyl type polymers which may be used to form my novel compositions are the polyvinyl acetates, polyvinylbutyral, butadiene copolymers, e.g. acrylonitrile-butadiene-styrene copolymers, the polyacrylonitriles, polybutadiene, polyaldehydes such as poly= oxymethylene, and the like. Additionally and even more preferably, one may incorporate the flame-retardant synergistic combinations mentioned above into such polymers as the styrene polymers, i.e. polystyrene, amethyl styrene polymers, etc. the ot-olefin polymers, such as the homopolymers and copolymers, etc. containing, as the major constituent, thereof, ethylene, propylene, including polyethylene, polypropylene and the like and the acrylate and methacrylate homopolymers and copolymers produced from monomers having the formula R O R wherein R is hydrogen or a methyl radical and R is hydrogen or an alkyl radical having from 1 to 6 carbon atoms, inclusive. Examples of monomers represented by Formula III include acrylic acid, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-amyl acrylate, t-amyl acrylate, hexyl acrylate and their corresponding alkyl methacrylates etc.

Also such poylmers as the nylons, e.g. adipic acid= hexamethylenediamine reaction products; the cellulosics such as cellulose acetate (and/or butyrate, etc.) cellulose nitrate; the polycarbonates, i.e. phosgene-Bisphenol A reaction products; the so-called impact polymers, i.e. rubber polymer blends such as blends of polystyrene with 5- 10% of butadiene-styrene, etc. and the like may be made flame-retardant by the incorporation therein of the diphosphine oxide-chlorinated hydrocarbon synergistic combinations discussed hereinabove.

Examples of other monomers which may be used to form the thermoplastic vinyl polymers encompassed by the present invention, polymerized either singularly or in combination with each other or with the other compounds set forth hereinabove, are such monomers as the unsaturated ethers, e.g., ethyl vinyl ether, diallyl ether, etc. the unsaturated amides, for instance, N-allyl caprolactam, acrylamide, and N-substituted acrylamides, e.g., N-methylol acrylamide, N-allyl acrylamide, N-methyl acrylamide, N- phenyl acrylamide, etc.; the unsaturated ketones, e.g., methyl vinyl ketone, methyl allyl ketone, etc.; methylene malonic esters, e.g., methylene methyl malonate, etc. and the like.

Other examples of polymers that may be employed are those of monomers set forth, for example, in U.S. Patent No. 2,510,503, issued June 6, 1950.

The production of thermoplastic resin compositions which are flame-retardant is of considerable commercial importance in that such articles as castings, moldings,

5. foamed or laminated articles, etc. are required, or at' least desired, to be resistant to fire and flame and to possess the ability to endure heat without deterioration. Typical illustrations of applications of such compositions include cast- 6 eificient is a modified version of that test identified as ASTM-D-635-56T. The specifications for this test are: a specimen, in length, 0.5 in width and 0.045 in thickness is marked at the 1" and 4" lengths and is then ings for live electrical contacts which should not be 5 supported with its longitudinal axis horizontal and its ignited by fiame or sparks, structural members such as transverse axis inclined at 45 to the horizontal. A Bunsen pipes, wall coverings, wall paneling, windows, etc.and such burner with a 1" blue flame is placed under the free end items as ash trays, waste baskets, fibers and the like. of the strip and is adjusted so that the flame tip is put in v The novel flame-retardant combinations claimed herein contact with the strip. At the end of 30 seconds, the flame may be added to the various polymers, as such, or as inis removed and the specimen is allowed to burn. If the dividual components, by any known method. That is to specimen does not continue to burn after the first ignisay, the flame-retardant components may be added to the tion, it is immediately recontacted with the burner for polymer as such or in combination by (1) milling the another 30 seconds. If, after the two burnings, the strip polymer and the components on, for example, a twois not burned to the 4" mark, the specimen is designated roll mill, in a Banbury mixer, etc. by (2) molding the as self-extinguishing. If the specimen is not burned to components and the polymer simultaneously, by (3) exthe 1 mark it is designated as non-burning. In the truding the polymer and components or by (4) merely modified test, the specimen is mils in thickness rather blending all the materials together in powder or liquid than the prescribed 0.045". form and thereafter forming the desired ultimate product. Additionally, the flame-retardant may be added during the 20 Example 1 production of the polymer, i.e. during the monomer polymerization, provided, however, that the catalyst, etc. To P f of P YP RY f added 5 Parts Of other conditions and other ingredients of the polymerizaethy p ybp p OXlde and 5 Parts of tion system are inert thereto. chlorinated paraffin wax containing 70% chemically com- It is also within the scope of the instant invention to ine or p i l f a 24 z9 21)- The incorporate such ingredients as plasticizers, dyes, pigsultant mixture is placed in a suitable blender and dryments, heat and light stabilizers, antioxidants, antistatic blended for 10 minutes. The blended product is then transagents, photochromic materials and the like into the the ferred to a melt-index apparatus (see ASTMD-1238 polymeric flame-retarded polymer compositions claimed T) Whlch is Prhflatfid t0 FOHOWiHg o mi te h i of aging, a 2.2 kg. weight is placed on the plunger and an The following examples are set forth for purpose of extrudate of 6-8 inches in length is obtained. This speciillustration only and are not to be construed as limitamen is marked and tested according to the above-enumertions on the present invention except as set forth in the ated fiame-retardance test. The results are set forth in appended claims. All parts and percentages are by weight Table I, below. unless otherwise specified. Various other flame-retardant combinations are then in- Any appropriate flame-retardance test may be used to corporated into various other resins according to Example determine the flame-retardant properties of any specifi 1 and comparisons are made between the resultant comcombination of diphosphine oxide and chlorinated hydropositions and control compositions. These results are also carbon material. One test I have found to be reasonably set forth in Table I, below.

TABLE i Diphosphine Oxide Flame- Ex. Chlorinated Hydrocarbon Per- Polymer test B R in Percent Results cent 1 Phenyl Phenyl 2 5 Chlorinated parafiin wax com- 5 Polypropylene Passed.

bined chlorine. Failed. Same as Ex. 1 10 Do. Hexachlorobenzene. 3. 5 Passed. Failed. Same as Ex. 4 7 Do. Perchloropentacyclodecane 7. 5 Passed. Failed. Same as Ex. 7 15 Do. Hexachlorocyc 5 Passed. Failed. Same as Ex. 10 10 Do. Chlorinated paraffin wax 50% com- 7 Passed.

bined chlorine. Failed. Same as Ex. 13 15 Do. White polyphenyl powder; distills, 5 Passed.

435-450 0.; softens, 170 C. Failed. Same as Ex. 16 10 .do Do. a,a-Dichloro-m-xylene... 7.5 P0ly(methylmeth- Passed.

acylate). do. Failed. Same as Ex. 19 15 do Do. Clear polyphenyl-resin; distills, 280- 4 Polyoxymethylene--. Passed.

335 0.; softens, 98-1055 C. Failed. Same as Ex. 22 10 0. Chlorinated parafiin wax containing 5 Passed.

40% combined chlorine. Failed. Same as Ex. 25 10 D0. Yellow, viscous polyphenyl oil; dis- 2 Passed.

tills, 365-390" 0.; pours, 10 C. Refractive Index 2 1.639-L641.

.... Failed.

5 D-line at 20 C.

I claim:

1. A flame-retardant composition composed of a combination of (1) a chlorinated hydrocarbon containing from about 40-80% of combined chlorine and having a boiling point of at least 200 C. and (2) a diphosphine oxide having the formula R o o R wherein R and R are, individually, selected from the group consisting of hydrogen, aryl (C C alkyl (C -C aralkyl (C7-Cn), cyanoalkyl (C 0 carboxyalkyl (C -C or carbamoylalkyl (C -C radicals and n is a Whole positive integer of from 1-4, inclusive, no more than one of R and R being hydrogen.

2. A flame-retardant composition according to claim 1 wherein (2) is ethylenebis(dipheny1)phosphine oxide.

3. A flame-retardant composition according to claim 1 wherein (2) is ethylenebis(dicyclohexyhphosphine oxide.

4. A flame-retardant composition according to claim 1 wherein (1) is a chlorinated paraffin wax.

5. A flame-retardant composition according to claim 1 wherein (1) is a polychlorinated cyclic hydrocarbon.

6. A flame-retardant composition composed of a thermoplastic polymer having incorporated therein a flameretarding amount of the composition of claim 1.

7. A flame-retardant composition according to claim 6 wherein said thermoplastic polymer is a polyolefin.

8. A flame-retardant composition according to claim 6 wherein said thermoplastic polymer is polyethylene.

References Cited UNITED STATES PATENTS 3,085,029 4/1963 Miles et a1. 10615 3,158,642 11/1964 Chapin 10615 MORRIS LIEBMAN, Primary Examiner. 

1. A FLAME-RETARDANT COMPOSITION COMPOSED OF A COMBINATION OF (1) A CHLORINATED HYDROCARBON CONTAINING FROM ABOUT 40-80% OF COMBINED CHLORINE AND HAVING A BOILING POINT OF AT LEAST 200*C. AND (2) A DIPHOSPHINE OXIDE HAVING THE FORMULA 